Dopamine, one of catecholamine neurotransmitters, plays an important role in many brain functions and behavioral responses. In this study, we developed a novel dual-signal whole-cell biosensor for the detection of dopamine through the generation of red fluorescent proteins and 6-decarboxylated betaxanthin pigments. The proposed system responses specifically to dopamine with a detection limit of 1.43 μM. Furthermore, a combination of dual output signals makes it possible to reduce the interference from other catecholamine neurotransmitters, including L-DOPA, epinephrine, and norepinephrine.